It is occasionally desirable to remove air from the interior of a building to the exterior of the building through a vent. In many cases, it is also desirable that air from the exterior of the building be prevented from entering the building through the same vent when air is not being removed from the interior of the building through the vent. It may also be desirable to prevent animals or debris from entering the building through the vent. One way of preventing air, animals, or debris from entering a building through a vent is through a vent cover. When air is being removed from the building, the vent cover is open, and when air is not being removed from the building, the vent cover is closed.